Prepare the Tzaziki Sauce. Grate the cucumber, sprinkle it lightly with salt, and place it inside a clean kitchen towel or cheesecloth. Squeeze firmly to wring out the excess moisture, then transfer the drained cucumber to a bowl and stir in the Greek yogurt, minced garlic, fresh lemon juice, and a drizzle of olive oil. Season with salt and ground black pepper.
Prepare the meatball mixture. Add the Ingredients for the meatball mixture to a bowl and use your hands to mix until well combined.
Form the meatballs. Form the meatballs with wet hands or a cookie dough scoop and place on a baking sheet. Place in the freezer for 30 minutes to firm the meatballs.
Cook the meatballs (OVEN METHOD). Preheat your oven to 400°F (200°C). Arrange the meatballs on a parchment-lined baking sheet, leaving space between each one, and bake for 15–20 minutes until they are golden brown and the internal temperature reaches 165°F.
Cook the meatballs (STOVE TOP METHOD). Heat olive oil in a large skillet over medium-high heat, then add the meatballs. Cook for 3-4 minutes per side until browned, and the internal temperature reaches 165 degrees F. You may need to work in batches to prevent overcrowding. Prepare the Greek salad. Divide the lettuce leaves, cherry tomatoes, cucumbers, red onion, and crumbled feta cheese into 4 bowls or plates. Drizzle with olive oil and lemon juice.
Arrange the meatballs. Arrange the meatballs on the Greek salad and serve with tzatziki sauce.